Network operators offer their subscribers a variety of different payment plans, in which different billing rates are geared to different types of content and services. For example, some types of content may be offered free of charge, others at a flat rate, and still others on a pay-per-use (or pay-per-view) basis. These sorts of billing models are commonly used in cable and satellite entertainment networks, in which the network operator offers multiple, simultaneous content channels and can readily identify which channel each subscriber is viewing at any given time.
This sort of differentiated billing is more complicated to implement in the context of Web-based content and service delivery. Content providers, such as Web site operators, can readily charge subscribers for access to their services; but network operators—who provide the communication link between the content providers and their suppliers—may find it difficult to identify the type of traffic on the link and charge their subscribers accordingly. Some network operators use deep packet inspection (DPI) to snoop inside transmitted packets, but DPI is only partially effective in classifying Web traffic. Therefore, network operators most commonly offer browsing packages in which billing is at a flat rate for all types of content or is based simply on connection time or data volume transmitted and/or received.